The present invention relates generally to photographic film developing equipment. More particularly, the present invention relates to an apparatus and method for developing a photographic emulsion carrier.
A related art apparatus and method for developing a photographic emulsion carrier are described in DE 43 04 907, corresponding to U.S. Pat. No. 5,414,484. To explain more clearly the problem on which the present invention is based, FIGS. 1A to 1C show a schematic representation of the apparatus known from the related art.
FIG. 1A shows an emulsion carrier 10, which is transported from a developer tank 12 to a fixer tank 14. The two tanks are separated from one another by a partition wall 16. Two rollers 18, 20 form a draining roller pair which, besides delivering the emulsion carrier 10, has the purpose of squeezing the processing fluid from the developer tank 12 from the emulsion carrier 10 prior to the emulsion carrier 10 entering the fixer tank 14. Guide devices 22 are used to feed the emulsion carrier 10 into an entry roller pair 24, 26 of the fixer tank 14. As can be seen from the representation in FIG. 1B, the developer fluid is not wiped off fully, so that a developer-fluid residue denoted by 28 remains adhering to an end section 30 of the emulsion carrier 10. Before the emulsion carrier 10 is immersed in the fixer fluid in the fixer tank 14, this residue 28 (see FIG. 1C) trickles down under the effect of gravity from the end section 30 of the emulsion carrier 10, along the emulsion carrier 10, towards its front region while forming drips 31 which may be in the range of several centimeters. Continued developing takes place in the vicinity of the drips 31, and this is clearly visible on the emulsion carrier 10 as dark regions with a higher optical density, after the complete developing process.
In conventional X-ray examinations, for example of an arm, a leg, the stomach etc., these dark regions are not a great problem since the body region to be examined is normally positioned in the middle of the exposure region. Faults due to the film processor at the edges of the X-ray film, for example scratches, density differences etc., are therefore acceptable to some extent, the diagnosis is not compromised.
The situation is very different for mammography, in which the diagnostic region extends as far as the outermost area of the film. In this case, no faults are therefore allowed. Degradations in the image quality due to the said drips can lead to cases of very serious misdiagnosis.
The present invention provides an apparatus and method for developing a photographic emulsion carrier, in such a way that it is possible to provide developed emulsion carriers with high imaging qualityxe2x80x94especially in the edge region as wellxe2x80x94so as to permit use for highly sensitive applications, for example mammography.
A first aspect of the invention provides an apparatus for developing a photographic emulsion carrier in a plurality of processing tanks, through which the emulsion carrier travels in succession, the apparatus including a rotatable roller, the photographic emulsion carrier having a front section and an end section and the roller being arranged in such a way that an end section of the photographic emulsion carrier comes into contact with the roller while travelling from a first processing tank to a second processing tank, wherein a direction of rotation of the roller is designed so that the roller wipes the end section in a direction away from the emulsion carrier.
A second aspect of the invention provides a method for developing a photographic emulsion carrier in a plurality of processing tanks, through which the emulsion carrier, which has a front section and an end section, travels in succession, comprising the following steps:
a) transporting the emulsion carrier from a first processing tank;
b) bringing the end section of the emulsion carrier into contact with a rotatable roller; and
c) rotating the roller in a direction such that the roller wipes the end section in a direction away from the emulsion carrier.
The solution according to the invention is based on the discovery that the formation of drips can be minimized if the fluid accumulating at the end section of the emulsion carrier and adhering there can be wiped off by a roller which rotates away from the emulsion carrier. This very significantly reduces the length of the drips which form and, with optimal design, even prevents any drips from forming.
It is particularly useful if the roller is part of a transport device which is present in any case, or if a roller separately added for the wiping process is coupled to the transport device for moving this roller.
Since the drips are formed on the side of the emulsion carrier where gravity acts, the roller is arranged in such a way that it touches the end section on this side.
If the wiping roller is part of a transport or squeezing device, or if its surface is coupled to the surface of a transport or squeezing roller, then this has the result that the wiping roller is always wetted with fluid. It has been found that this wetting has a positive effect in terms of minor build-up of the fluid accumulating at the end section of the emulsion carrier. This wetting can also be achieved by direct or indirect contact of the roller surface with a roller turning in the bath fluid.
The apparatus according to the invention may also comprise a holder element which can support the emulsion carrier during the wiping. This ensures that the emulsion carrier, especially its end section, is not missed during the wiping process.
The holder element can be produced by configuring one of the guide apparatuses, which are in any case provided, for forwarding the emulsion carrier from one processing tank to the next, in such a way that it can fulfil the function of the holder element.
Of course, the invention also comprises the option that the emulsion carrier may be sent, prior to introduction into the next processing tank, to a separate station in which the wiping process is carried out with a separate roller. It is useful, however, to design the elements which are present in any case, such as transport rollers and guide apparatuses, in such a way that a gap is formed between a roller of the transport device and a guide apparatus serving as the holder element, the guide apparatuses forwarding the emulsion carrier so that its end section enters the gap for the wiping to be carried out.